Abstract: A few key issues influencing the safety of high earth-rockfill dams are discussed, and the research progress in recent years is reviewed. The factors which influence the scale effects of coarse-grained materials are analyzed. Both the experimental tests and the numerical simulations on the custom-made granular materials, besides the back analysis of the actual deformation parameters of embankment dams are carried out to study the scale effect on deformation parameter of rockfills. Then a method is proposed to determine the on-site mechanical parameters of coarse-grained materials according to laboratory test parameters. The test methods to determine the long-term deformation characteristics of coarse-grained materials and the development of those methods are discussed. The evolution laws of rheological deformation with time are studied, and a logarithmic power